Fewer than 10% of the people prosecuted for terrorism in the United States since the September 11 attacks were convicted of crimes related to that ornational security, according to a study conducted by the Washington Post.

Of those 39 people, few had any connection to al-Qaida while the remaining 90% were acquitted or convicted of lesser crimes such as immigration violations or making false statements, the study shows.

The report emerged as President George Bush travelled the country to encourage Congress to renew the Patriot Act, the controversial attempt to counter terrorism by boosting surveillance powers.

``Federal terrorism investigations have resulted in charges against more than 400 suspects, and more than half of those charge have been convicted,'' Mr Bush told the Ohio State Highway Patrol Academy on Thursday.

But, according to the Washington Post, the vast majority of those arrested were eventually convicted of only minor violations for which they were either deported or received relatively short sentences.

The median sentence for all of the cases, related to terrorism or not, was 11 months. Of those who were convicted on terrorist charges, most were involved not with al-Qaida but causes and crimes such as Colombian drug cartels, Rwanda's civil war or support for Palestinian groups.